Force is about balance and enforcing contracts. The Bestiary would seem to imply that Force is also about making sure the natural laws of physics, as well as The Compact, are maintained despite attempts to circumvent them. Dagda's angels spend a lot of their time fighting Ceridwen's demons, as Ceridwen tries to circumvent the natural laws most often. As magic is about bending the rules, Force could perhaps be seen as more anti-magic than magic.
The ability to send summons home does seem to fit Force. However, Force is so concerned with fairness that I don't think it is appropriate for it to banish your rivals summons unless it also banishes your own.
Cipi should really have 2 p's, making it Latin for a stake, pale, grave marker, or especially (when plural) palisades. Kael was afraid people would confuse them with the Hippi if he spelled it right though.
After the Bestiary came out I decided to change my Force III spell to Summon Runewyn. The Rumewyn unit is magic immune, but more importantly can target Arcane units in stacks of stronger defenders, has a bonus vs arcane units, and has a python post combat call that can remove random promotions from spells, spell spheres themselves, and even channeling promotions from the enemy unit that defeats it.